The present invention relates to a radio communication device and a user authentication method using user authentication passwords.
In recent years, attention has been paid to radio communication systems adapted for personal areas, such IrDA, Bluetooth, HomeRF, etc. Particularly, Bluetooth and HomeRF have merits of no directivity and high transparence over infrared communication systems, such as IrDA, and are greatly expected to develop and find wide application in the future. The Bluetooth is short-haul radio communication standards and establishes radio communications within 10 m or 100 m using the ISM (Industrial Science Medical) band of 2.4 GHz band. The Bluetooth adopts frequency-hopping spectrum-spreading techniques and allows for connection of up to eight devices through the use of time-division multiplexing techniques.
In addition to allowance for simultaneous connection of multiple devices, the radio communication systems, such as Bluetooth, HomeRF, etc., make a great feature of a relatively long transmission distance of, say, 10 to 100 m in comparison with the infrared communication systems, such as IrDA. This provides an advantage of ease of handling, but on the other hand sufficient attention must be paid to assure system security and confidentiality.
Conventional security systems for radio communication systems include the radio terminal security system as described in Japanese Patent No. 2872996 and the one-time password system as used in the Internet.
These security systems include electronic keys and radio terminals and prohibit successive use of the same key to increase security, thereby providing increased safety against loss and theft of the key.
Next, the user authentication system used in the Bluetooth will be described.
The user authentication system used in the Bluetooth is subject to two: a unique password set up on each device (called a PIN (Personal Identification Number) code) and an encryption key (called link key) created by the password and an ID code unique to the device (information, such as a 48-bit address, assigned by IEEE). This system will be described in brief below with reference to a flowchart shown in FIG. 7.
Consider now the case where a device A makes access to a device B. The device A makes a request for connection to the device B (step A1), whereupon the device B checks the presence or absence of the link key to see if the connection to the device A is set up for the first time (step A2). That is, the device B is stored with a list of link keys besides PIN codes. This list is a table of unique addresses of devices connected so far to the device B and corresponding link keys. An example of this table is illustrated in FIG. 8.
In the situation in which the device A and the device B are connected for the first time, the device A is required to input the PIN code of the device B. Upon receiving the PIN code from the device A, the device B checks it for validity (step A3). If the PIN code is authenticated, then the device B establishes a link (step A4) and creates a link key for the device A (step A5). The resulting link key is entered into the list together with the unique address of the device A (step A6).
If, on the other hand, the device A was sometimes connected to the device B in the past, since the link key has already been entered into the table in the device B, authentication is made through that link key (step A7).
The Bluetooth provides authentication using the PIN code unique to each device and the link key based on the PIN code. The PIN code, while being unique, can be altered by the device user into any other string of characters.
The security system disclosed in Japanese Patent No. 2872996, the one-time password system in the Internet and the user authentication system in the Bluetooth can be said to be password management and authentication systems intended to provide only increased security.
The use of the user authentication system in ad hoc network environment causes problems as described below.
As an application of the user authentication system used in the Bluetooth, consider a table conferencing system made up of a plurality of information devices. Each individual device is required to establish a fiduciary relationship based on the above user authentication system with the others.
However, in order for each individual user having his own private PIN code to ensure the security of his own device, it is desirable to adopt a method involving creating a temporary PIN code and changing it to the original private PIN code at the termination of the table conferencing rather than establishing the fiduciary relationship by informing the other users of the private PIN code.
To adopt the user authentication system as described above, therefore, it is required to take the following steps:
S1: Each individual user sets up a temporary PIN code on his own device and informs the other users of that PIN code.
S2: Holds table conferencing.
S3: At the termination of the conferencing, each individual user makes a change from the temporary PIN code to his original private PIN code.
With the above approach, however, not only does it take long to set up the PIN code, but also the security level is considerably lowered in the event that the user forgot to make a change from the PIN code to the original PIN code; for, in such case, the temporary PIN code will come to be used successively.